Such multiple beam display tubes are frequently used to display alphanumeric and/or other visual pattern information. Typically, the tubes utilize a plurality of closely spaced electron beams which are arranged in a single vertical column array. The beams are deflected together across the screen and are repeatedly turned on and off so as to form "dots" on the screen at respective scanning positions. In order to form desired characters or other patterns, logic circuitry selectively controls each beam at each scanning position and the resulting arrangement of "dots" forms the desired pattern. Such multiple beam cathode ray tubes have greater bandwidth than single beam tubes, which enables them to display more information at suitable brightness than the single beam type.
The conventional multi-beam tube described above, however, suffers from several problems. First, because the beams are very close together and actually may touch each other, mutual repulsion results, which may cause the top and bottom beams to be deflected upwardly and downwardly respectively when the beams are turned on. Second, since the beams are located very close to each other there is little space to build and mount the grids which control the intensity of the beams. While making the beams smaller in diameter might help this problem, reduction in beam size cannot be accomplished without a corresponding dimunition in beam brightness. A third problem which exists with the conventional straight line beam array is beam intermodulation. That is, because of the closeness of the beams, the control grid of one beam may affect or intermodulate the current of another beam, thereby diminishing effective grid control.